Fuel system for a gas turbine engine

Abstract

A system for automatically transferring the fuel from one or more engine fuel manifolds directly to the engine fuel tank(s) during engine shutdown using an ejector pump has been presented. A checkvalve, which may be integrated with the ejector pump, is also used. A metering valve initiates fuel flow shutoff and is used in the draining of the fuel manifolds, thereby eliminating the need for an additional solenoid dedicated mainly to the shutoff function. The shutoff and pressurizing valve provides flow division between manifolds and manifold drain for systems having multiple manifolds. The bypass valve is used to turn the motive flow and / or manifold drain functions on and off as a function of engine speed at start and shutdown.

Description

FIELD OF THE INVENTION[0001]This invention pertains to gas turbine engines, and more particularly to a system for transferring fuel from the engine manifolds of a gas turbine engine at engine shut down.BACKGROUND OF THE INVENTION[0002]In many gas turbine engines, the fuel system for regulating the flow of fuel to the combustion chamber consists of one or more fuel nozzles arranged in the combustion chamber, a fuel pump for pressurizing fuel from the fuel supply, a fuel metering unit for controlling the flow of fuel to the fuel nozzles and one or more fuel manifolds fluidically connecting the fuel metering unit to the fuel nozzles.[0003]During engine start-up, fuel is pumped from the fuel supply to the fuel metering unit by the fuel pump and, once a sufficient start-up pressure is attained, the pressurizing valve of the fuel metering unit opens and fuel is supplied to the fuel nozzles via the fuel manifold. Thereafter, the metering valve of the fuel metering unit modulates the rate o...

AI Technical Summary

Benefits of technology

[0009]In one embodiment, the checkvalve is located in the suction line of the system. In a second embodiment, the checkvalve is located in the injector inlet line and is integrated with or becomes part of the ejector pump. The system has an electro-hydraulic servovalve that is used as the metering valve and also initiates fuel flow shutoff by closing the metering valve port and switching P2 pressure to Pb. This equalizes the pressure across the two ends of the pressurizing valve, thereby allowing the pressurizing valve spring to close the pressurizing valve. The use of the metering valve to initiate shutoff eliminates the need for an additional solenoid. The closed pressurizing valve ports both manifolds to the suction side of the injector and allows the ejector to suck the fuel out of the manifolds upon shutdown.

[0011]The pressurizing and shutoff valve is also used for flow division between manifolds on engines that have more than one manifold and as a valve to open up a flow path from the manifold(s) to the suction port of an ejector pump. The ejector pump is supplied with flow from a port on the bypass valve. This flow is used during engine operation to operate a fuel tank ejector pump in the fuel tank. The checkvalve is located in the suction line or the inlet line of the ejector pump. The checkvalve prevents ejector leakage into the engine manifolds when the engine is shutdown.

Problems solved by technology

Coking of the residual fuel is a fire hazard and can lead to blockages in engine fuel injectors, which results in shorter injector life and can harm engine performance.

While the Dalton patent provides a unique system for pumping the residual fuel from an engine manifold after the engine is shut down, it is a relatively complex system.

These features add to the overall complexity and may decrease the reliability of the system.

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